多尺度DEM提取河流比降的对比分析

Contrastive Analysis of Stream Gradient Based on Multiscale DEM

研究旨在用DEM计算河流比降,分析DEM分辨率与阈值对比降的影响,并提取最佳分辨率与最佳阈值。以延河流域的ASTER GDEM和SRTM3 DEM为原始数据源,利用Arc GIS分别提取60、150、200、300 m分辨率下延河流域的主河道,并据此计算流域平均比降。结果表明:延河的平均比降为3.39‰;DEM分辨率与汇流阈值对比降影响较大,当DEM分辨率小于150 m时,比降随阈值增大而减少;DEM分辨率大于150 m,比降逐步增大。延河流域河流比降分析的DEM分辨率不宜超过150 m,其中DEM分辨率为90 m时,计算的比降结果较为符合延河流域实际情况;DEM分辨率为30、60、90、150、200、300 m时,计算比降的最佳阈值分别为65000、60000、30000、70000、40000、20000;利用85%的主河道折线段信息,进行比降计算,其结果接近真实值。研究实现了基于DEM的河流比降计算,有助于DEM在水文学等流域的应用。

The aim of this study is to calculate river gradient by DEM, analyze the influence of DEM resolutionand threshold on gradient and extract the best resolution and optimal threshold. The ASTER GDEM and SRTM3 DEM of Yan River were selected, the drainage line was extracted by Arc GIS under the resolution of60, 150, 200 and 300 m, and then the stream gradient was calculated. The results showed that the averagestream gradient was 3.39‰, gradient was affected by DEM resolution and threshold. When the DEM resolutionwas less than 150 m, the gradient decreased with the increase of threshold; when the resolution was greaterthan 150 m, the gradient increased gradually. Therefore, the resolution of DEM should not exceed 150 m, whenthe resolution was 90 m, the results accorded with the physical situation of Yan River; when the resolution ofDEM were 30, 60, 90, 150, 200 and 300 m, the optimal threshold were 65000, 60000, 30000, 70000, 40000 and 20000, respectively. The results calculated with 85% drainage line polyline information were close to thetrue value. In this study, the calculation and the analysis of stream gradient of Yan River are beneficial for theapplication of DEM in hydrology.